1. Field of the Invention
The present invention relates to a fly sewing machine for sewing plural flies made of fabric piece such as flies of trousers to a long slide fastener chain continuously.
2. Description of the Related Art
A machine for sewing plural flies to a long slide fastener chain has been disclosed in, for example, Japanese Patent Application Publication (JP-B) No. 63-009878. According to this machine, each fly is supplied to that sewing machine successively through a supply section. A series of flies are carried to the sewing machine by the supply section such that they are arranged in order in conditions in which ends thereof keep contact with each other even if lengths of the flies are different, and sewed successively. The supply section includes plural pairs of drive rollers and supporting rollers which constitute a driving nipper, so that a series of flies carried to the supply section are sent by the driving nipper. One of the drive rollers that is located on an uppermost upstream side rotates fastest and carrying speed decreases as it goes to a downstream side. Further, rotation speed of the drive roller located on a bottommost downstream side is set higher than sewing speed of the sewing machine. As a consequence, before sewing operation of a preceding fly is completed, a front end of a following fly arrives at a rear end of the preceding fly.
A supporting roller is installed to a housing having a guide surface in which a gap of a specified size is formed and urged against an opposing drive roller slightly, so that it carries each fly by a guide of the gap. By passing the fly through this gap, the front end of a following fly is protected from being bent or overlapping the rear end of a preceding fly, so that it can make contact with the rear end of the preceding fly.
Fabrics having various thicknesses from a relatively thick fabric (denim for jeans) to a thin fabric. The sewing machine disclosed in JP-B No. 63-009878 can sew flies composed of same fabric continuously by sending a following fly such that it overtakes the rear end of a preceding fly and making contact therewith. On the other hand, a sewing workshop is demanded to sew a series of flies to a long slide fastener chain using a same sewing machine regardless of the thickness of fabric of the flies. However, if gaps formed vertically in a fly carrying passage are unchanged when it is intended to continuously sew flies composed of various thicknesses as described previously, when the front end of a following fly makes contact with the rear end of a preceding fly, the front end of the following fly overlap the preceding fly or an end section in contact is folded.
To prevent this, the gap in a vertical direction of the fly carrying passage needs to be adjusted corresponding to the thickness of a fabric. Executing this adjustment of the gap each time when the thickness of fabric changes leads to complicate a preparatory work for sewing, which never goes along with the above-described demand for the sewing workshop. Further, unless the adjustment of the gap is carried out accurately corresponding to the thickness of fabric, the front end of the following fly may overtake and ride over the preceding fly or the end section in contact may be folded. Further, if a kind of the fly changes, the carrying speed of the fly also changes, because friction of the fabric surface changes depending on a difference of weaving of fabric. To meet this change of friction, a difference in rotation speed between respective drive rollers disposed in a fly supply section needs to be adjusted with high accuracy. In recent years in which a trousers sewing manufacturer handles sewing work of multiple kinds of fabrics, it has been highly demanded to shorten adjustment time for a unit required at a time of fabric change-over as much as possible.
Further, it is difficult for the fly sewing machine disclosed in JP-B No. 63-009878 to sew a curved fly after serging with an end portion cut into a circular shape and serged. That is, although the sewing machine of JP-B No. 63-009878 sews flies continuously since end surfaces thereof kept in contact with each other after a following fly catches up with a preceding fly, it is very difficult to sew flies whose contact end is not linear like the curved fly continuously to a fastener chain in a condition in which they are in contact with each other because the carrying direction changes when the flies are carried. Further, because a thickness of a thread is added to a serged portion, it comes that a difference occurs in thickness between the serged portion and fabric main body. In a condition in which a difference exists in thickness of the fabric of a single fly, the carrying speed cannot be kept constant, so that flies cannot be carried continuously in a stable condition such that they are kept in contact with each other or sewed down.